We are continuing the exploitation of our sensitive assay for tissue ionophores to study the pharmacokinetics of oral ionophore absorption in a variety of species. Particular emphasis will be placed on distribution in the chicken and sheep in view of the widespread use of ionophores as livestock feed additives which may possibly expose man to these powerful cardiotonic agents. The results will be correlated with a variety of tissue response to ionophores: coronary dilitation, increased myocardial contractility and the exocytotic dicharge of hormones: catecholamines, glucagon, insulin, etc. The interaction between catecholamines which cause myocardial "oxygen wasting" and ionophores which increase myocardial work/O2 consumed will be examined, especially the interaction between the two agents. The rise in efficiency of cardiac energy transduction will be examined as the possible basis for the ability of ionophores to raise the efficiency of feed conversion in poultry, ruminents and swine. The molecular basis of ionophore function will be studied by ascertaining the effects of varying solvent polarity on ionophore-cation affinity and ionophore conformation by the techniques of circular dichroism and nuclear mangnetic resonance.